Lady Calcula was the wife of Colonel Nasgard and the mother of Yarvell and Davros (the latter by her lover, Councillor Quested). She hated her sister-in-law Tashek for knowing the truth about Davros' parentage, who in turn hated Calcula for not revealing the truth to her husband and for favoring Davros over Yarvell.
Calcula hired Tutor Magrantine to teach Davros whatever he wished to learn, planted a bomb to kill Nasgard and Tashek (perceiving them as dangers to her son), and manipulated Quested, whom she worked for as his personal assistant, to have Major Brogan arrested and executed as a traitor. (BFD: Innocence)
Calcula contested the terms of Nasgard's will, which stated that she would not have access to Davros's trust fund until he got married. She and Yarvell learned of Davros's part in the mission to destroy a new Thal weapon development facility, and afterwards tricked Yarvell into revealing her part in compromising the mission. She then drowned her in the swimming pool at their home in fury. (BFD: Purity)
Calcula eventually took charge of the Kaled Military Youth, with Section Leader Fenn as her assistant. When Fenn tricked her into granting him access to Davros's laboratory, then attempted to destroy his work, she turned on Davros's latest invention, exposing them both to massive doses of radiation and causing them to mutate. Before dying, she told her son to dedicate himself to destroying all who would destroy him. She may have been mutated into a very early Dalek creature as her voice resembled a Dalek and Davros said to her "I will make the universe fear what you have become". This turned out to be true as Davros put her remains in an early travel machine and used it as a security guard for his lab. (BFD: Corruption)
When Davros was laying unconscious and near death when Thals shelled his laboratory, he heard his mother's voice, urging him to survive and live on. (BFD: Corruption)
After Davros was rescued from the Thals by Nyder, he hallucinated conversing with his mother and sister. (BFD: Guilt)